12.7.15 GIMPLE_OMP_FOR

Build a GIMPLE_OMP_FOR statement. BODY is sequence of statements
inside the for loop. CLAUSES, are any of the OMP loop
construct's clauses: private, firstprivate, lastprivate,
reductions, ordered, schedule, and nowait. PRE_BODY is the
sequence of statements that are loop invariant. INDEX is the
index variable. INITIAL is the initial value of INDEX. FINAL is
final value of INDEX. OMP_FOR_COND is the predicate used to
compare INDEX and FINAL. INCR is the increment expression.